1. Field of the Invention
This invention pertains to seismic surveying gathering systems and more particularly to such a system employing radio communications between the field data acquisitions units and a central recording station wherein part of the electronics for the central station is carried as an electronic package by a tethered blimp.
2. Description of the Prior Art
The use of radio links for the communication network required between remote or field data acquisition units for detectors and the command or central data gathering and recording station is becoming increasingly popular with the increasingly difficult geographical terrains now being encountered. That is, with the increasing pressure to survey for oil and gas supplies, more and more difficult and remote areas of the world are being explored for this purpose. Conventional cable connections previously employed are becoming increasingly difficult or impractical to use.
The most effective gathering system employing radio communications uses an airborne-installed central station, such as described in patent application Ser. No. 48,393, filed June 14, 1979, and commonly assigned with the present application. The detector arrays which are uniformly located for regular and complete coverage, often locate some individual detectors in ground swells, in swamps, behind hills and otherwise makes line-of-sight radio communications difficult to impossible without the use of an airborne central station. With an airborne central station, however, line-of-sight is assured and the high frequencies that are allocated for use by the FCC can be utilized.
However, it is well known that using an airplane is expensive. Moreover, airplanes are complicated machinery and are subject to maintenance and repair problems that result in sometimes more than occasional down time. Furthermore, operating an airplane can be hazardous and should a plane crash, there would be expected long delays in running a survey as well as the expense of replacing the aircraft and the equipment.
Electronics have been carried by unmanned airborne vehicles in applications where it was advantageous to have a high elevation communications terminal and other electrical components. For example, weather balloons carry instruments for sampling the environment and transmitting certain findings back to a land-based or ground receiver. Such balloons are, of course, not tethered and are not controlled or powered or signalled in any way through the use of cables. Moreover, such balloons are not controlled as to location nor do they operate intimately with an electronics package which is partly ground based and partly air-launched. Furthermore, such a balloon, if tethered, would tend to lie over at an acute angle to the earth in steady winds and would not attain the desirable high altitude and nearly vertical attitude of an aerodynamically shaped blimp.
Balloons have been used to enhance communications, particularly voice communications, in some military applications. Such balloons have carried only the rather long wire antennas that are required when communicating at relatively low frequencies, for example, below 30 MHz. It is not believed that any such balloons have carried appreciable electronics controllable from the ground, nor that they have had components including a small battery to optimize operations while minimizing the effects of power losses both to and from the balloon-carried components. Moreover, no known balloon antenna system has been operable in the 70+ MHz range contemplated for the system described herein.
Therefore, it is a feature of the present invention to provide an improved seismic survey gathering system wherein part of the central station electronics can be airborne without the use of an airplane.
It is another feature of the present invention to provide an improved seismic survey gathering system utilizing a blimp for carrying some of the electronic elements of the central station.
It is still another feature of the present invention to provide an improved seismic survey gathering system whereby the central station thereof is heliportable, and in which part of the central station is launchable via a tethered blimp, thereby providing the advantages of an airplane-installed central station without the disadvantages of high cost of operation and unreliability of airplane availability.